From 168817476f85e8dbc04c06691a73a7d75c4858d5 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Thu, 10 Mar 2022 21:17:17 +0800
Subject: ...

---
 src/platform/Color.cpp | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

(limited to 'src/platform/Color.cpp')

diff --git a/src/platform/Color.cpp b/src/platform/Color.cpp
index b39865a8..dd1736ca 100644
--- a/src/platform/Color.cpp
+++ b/src/platform/Color.cpp
@@ -1,5 +1,7 @@
 #include "cru/platform/Color.h"
 
+#include <algorithm>
+#include <cmath>
 #include <cstdint>
 #include <gsl/gsl>
 #include <optional>
@@ -245,4 +247,82 @@ std::optional<Color> GetPredefinedColorByName(StringView name) {
     return std::nullopt;
   }
 }
+
+HslColor::HslColor(const Color& color) {
+  float rgb[3] = {color.red / 255.f, color.green / 255.f, color.blue / 255.f};
+  float& r = rgb[0];
+  float& g = rgb[1];
+  float& b = rgb[2];
+
+  int max_index = 0;
+  int min_index = 0;
+
+  if (r > g) {
+    max_index = r > b ? 0 : 2;
+    min_index = g < b ? 1 : 2;
+  } else {
+    max_index = g > b ? 1 : 2;
+    min_index = r < b ? 0 : 2;
+  }
+
+  float max = rgb[max_index];
+  float min = rgb[min_index];
+
+  float delta = max - min;
+
+  if (delta == 0) {
+    h = 0.f;
+  } else if (max_index == 0) {
+    h = 60.f * std::fmod((g - b) / delta, 6.f);
+  } else if (max_index == 1) {
+    h = 60.f * ((b - r) / delta + 2.f);
+  } else {
+    h = 60.f * ((r - g) / delta + 4.f);
+  }
+
+  l = (max + min) / 2.f;
+
+  s = delta == 0 ? 0 : delta / (1 - std::abs(2 * l - 1));
+
+  a = color.alpha / 255.f;
+}
+
+HslColor::operator Color() const {
+  Expects(h >= 0.f && h <= 360.f);
+  Expects(s >= 0.f && s <= 1.f);
+  Expects(l >= 0.f && l <= 1.f);
+
+  float c = (1 - std::abs(2 * l - 1)) * s;
+  float x = c * (1 - std::abs(std::fmod(h / 60.f, 2.f) - 1));
+  float m = l - c / 2;
+
+  float rgb[3] = {0.f, 0.f, 0.f};
+
+  if (h >= 0.f && h < 60.f) {
+    rgb[0] = c;
+    rgb[1] = x;
+  } else if (h >= 60.f && h < 120.f) {
+    rgb[0] = x;
+    rgb[1] = c;
+  } else if (h >= 120.f && h < 180.f) {
+    rgb[1] = c;
+    rgb[2] = x;
+  } else if (h >= 180.f && h < 240.f) {
+    rgb[1] = x;
+    rgb[2] = c;
+  } else if (h >= 240.f && h < 300.f) {
+    rgb[0] = x;
+    rgb[2] = c;
+  } else if (h >= 300.f && h < 360.f) {
+    rgb[0] = c;
+    rgb[2] = x;
+  }
+
+  for (int i = 0; i < 3; ++i) {
+    rgb[i] += m;
+    rgb[i] *= 255.f;
+  }
+
+  return Color(rgb[0] + 0.5f, rgb[1] + 0.5f, rgb[2] + 0.5f, a * 255.f + 0.5f);
+}
 }  // namespace cru::platform
-- 
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